USER_EXTENTS

Extents comprising segments owned by the user

Columns
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SEGMENT_NAME
Name of the segment associated with the extent
PARTITION_NAME
Partition/Subpartition Name,if any,of the segment
SEGMENT_TYPE
Type of the segment
TABLESPACE_NAME
Name of the tablespace containing the extent
EXTENT_ID
Extent number in the segment
BYTES
Size of the extent in bytes
BLOCKS
Size of the extent in ORACLE blocks